The present invention relates to a method of controlling an automotive powertrain and in particular to entering and exiting a parallel mode of operation for a powersplit powertrain.
An automotive vehicle may use a powersplit hybrid electric powertrain. Included in the powersplit powertrain is an electric generator, which may also alternatively operate as an electric motor. The powersplit powertrain may be operated in a plurality of modes, including negative powersplit, positive powersplit, and parallel modes. In the positive powersplit mode the generator charges a battery. In the negative powersplit mode the generator operates as a traction motor producing a torque to propel the vehicle. In the parallel mode the generator is braked from rotating, which allows the vehicle to be propelled by a combined torque produced by the engine and a second electric motor. A clutch may be used to brake the generator so that the powertrain may operate in the parallel mode.
However, entering the parallel mode requires the clutch to brake the generator from rotating and exiting the parallel mode requires the clutch to release the generator to rotate.